A structural steel for
welding with ultra-great heat input and a manufacturing method thereof. The invention belongs to the technical field of high-strength steel plate for
welding. The steel plate comprises, by
mass percent, the following chemical compositions: 0.03-0.12 wt% of C, 0.01-0.30 wt% of Si, 1.2-2.0 wt% of Mn, not more than 0.015 wt% of P, not more than 0.008 wt% of S, not more than 0.03 wt% of Al, not more than 0.5 wt% of Cr, not more than 0.5 wt% of Mo, not more than 0.03 wt% of Nb, 0.005-0.03 wt% of Ti, 0.01-1.0 wt% of Ni, 0.01-1.0 wt% of Cu, 0.002-0.007 wt% of N, and 0.001-0.006 wt% of O, and also comprises one or more elements selected from Mg, Ca, B, Zr, Ta, or REM with the balance being Fe and unavoidable impurities, and the carbon equivalent of the steel plate is less than 0.40%. The type, size and quantity of the inclusions are controlled by controlling the
alloy addition method during the refining phase, and the steel plate for
welding with great heat input is manufactured by controlled rolling and controlled cooling process. The advantages are that the steel plate has high strength and good
toughness, can endure a welding heat input of 400-1000 kJ / cm, still has excellent low-temperature
toughness after welding, and has an average
impact energy value of above 70 J at -20 DEG C.